Anatomy of the human heart: Educational resources

Ahmed Raza

Written by Linda Ikwuagwu, a registered perioperative nurse with over six years of experience in medical-surgical, trauma, community health, and humanitarian services. She is BLS and ACLS certified and dedicated to improving patient care and wellness.

The primary function of the human heart is to pump blood into the arteries, which carry oxygen and nutrients to all the body’s tissues. The heart is located in the center of the chest, with its apex toward the left. It is the hardest-working muscle in the body, as it beats nonstop. Suppose we want to understand how the heart performs its vital role. In that case, we will first examine its structure.

The heart is a muscular pump with four chambers and valves. The two chambers at the top of the heart are the right and left atria. The two bottom chambers are the ventricles. The atria receive blood that returns from the different parts of the body, while the ventricles pump that blood back to all body tissues. Valves that separate the atria from the ventricles are called the atrioventricular valves. There are two: the tricuspid on the right and the mitral on the left. Valves at the ventricular outlets are called semilunar valves. The two semilunar valves are the pulmonary and the aortic.

The heart wall consists of three layers: the outer epicardium, the middle myocardium, and the inner endocardium. The epicardium and endocardium are thin layers. The myocardium forms the main bulk of the heart and comprises cardiac muscle fibers. The outermost layer that surrounds the entire heart is called the pericardium. Vessels that carry blood away from the heart to the body are called arteries, while those that bring it back are called veins. The largest artery is named the aorta. It arises from the left ventricle.

The heart has an electrical system that originates and transmits cardiac impulses that cause it to beat. The system is made up of nodes and conducting fibers. If a person were to close their fist, slightly open it, and close it again in rhythmic motion, this would be a simplistic display of the beating heart. The human heart is similar in size to the human fist. It weighs around 8 to 10 ounces in females and 10 to 12 in males.

The events that take place in the heart between successive heartbeats constitute the cardiac cycle. Such events include valves’ opening and closing and the chambers’ contraction and relaxation. The cardiac cycle is split into two phases: systole and diastole. During systole, the ventricles contract and push blood into the arteries. During diastole, the ventricles relax and receive blood from the atria.

Conclusion

The human heart is a vital organ that continuously pumps blood throughout the body, supplying oxygen and nutrients to tissues. Its complex structure, consisting of four chambers, valves, and an electrical conduction system, enables efficient circulation. The cardiac cycle, which includes systole and diastole, ensures rhythmic blood flow. Understanding the heart’s anatomy is fundamental to appreciating its critical role in sustaining life and maintaining overall health.

Citations

Minnesota, U. of. (2021). Atlas of Human Cardiac Anatomy. https://www.vhlab.umn.edu/atlas/

Structure of the heart. Structure of the Heart

SEER Training. (2011). https://training.seer.cancer.gov/anatomy/cardiovascular/heart/structure.html

Pollock, J. D. (2022, October 3). Physiology, cardiac cycle. StatPearls [Internet]. https://www.ncbi.nlm.nih.gov/books/NBK459327/
Libretexts. (2021, July 8). 17.2: Location, size, and shape of the heart. Biology LibreTexts. https://bio.libretexts.org/Courses/West_Hills_College_-_Lemoore/Human_Anatomy_Laboratory_Manual_%28Hartline%29/17%3A_Cardiovascular_System_-_The_Heart/17.02%3A_Location_Size_and_Shape_of_the_Heart
U.S. National Library of Medicine. (2023, November 21). In brief: How does the blood circulatory system work?. InformedHealth.org [Internet]. https://www.ncbi.nlm.nih.gov/books/NBK279250/.

See also our page on heart abnormalities for more information on how the heart works. For getting certified, check our 100% online and accredited ACLS course.